scholarly journals Three-dimensional Reconstruction of Coronal Plasma Properties from a Single Perspective

2021 ◽  
Vol 922 (2) ◽  
pp. 109
Author(s):  
Joseph Plowman

Abstract Much of our understanding of the state of coronal plasmas comes from observations that are optically thin. This means that light travels freely through the corona without being materially affected by it, which allows it to be easily seen through, but also results in a line-of-sight degeneracy that has previously thwarted attempts to recover the three-dimensional structure of the coronal plasma. However, although the corona is disorganized in the line-of-sight direction, it is highly organized in the field-aligned direction. This paper demonstrates how to exploit this organization to resolve the line-of-sight degeneracy in the plasma properties using a suitable magnetic field structure. This allows, for the first time, the two-dimensional optically thin plasma observations to directly drive the three-dimensional plasma reconstruction throughout an entire active region (or larger). A preliminary investigation with a potential field is shown, finding a solution which clearly resembles the real solar data, even with a single perspective. The results indicate that there is ample information in the resulting residuals that can be used to refine the magnetic field structure, suggesting that these residuals can in turn be used to directly constrain the magnetic field extrapolations used in the reconstruction. The paper concludes with a discussion of how these residuals can in turn be used to directly drive the magnetic field extrapolations.

2001 ◽  
Vol 203 ◽  
pp. 393-395
Author(s):  
Y. Hanaoka

The three-dimensional structure of the magnetic field in the source region of CMEs is the key to understand how the stored magnetic energy eventually causes an eruption. A CME accompanied by a filament eruption on 2000 February 26-27 is particularly a good event to study the three-dimensional magnetic field structure. This event was very well observed with the EIT and LASCO of SOHO and the SXT of Yohkoh, and shows the following clues of the magnetic field structure which caused the CME. (1) The filament had a helical structure before the eruption and it was kept throughout the eruption. (2) The coronal loop structure shows that this event was an eruption of a part of the quadrapolar magnetic field structure consisting of two active regions. In this proceeding, we present a brief overview of the event.


1990 ◽  
Vol 140 ◽  
pp. 198-200
Author(s):  
R. Beck ◽  
E.M. Berkhuijsen

A three-dimensional, arc-like structure in the magnetic field was found coming out of the plane of M31. This structure may be the first Parker-Jeans instability observed in an external galaxy.


2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Tetsuya Zenko ◽  
Tetsuya Nagata ◽  
Mikio Kurita ◽  
Masaru Kino ◽  
Shogo Nishiyama ◽  
...  

Abstract A new method for measuring the global magnetic field structure of the Galactic plane is presented. We have determined the near-infrared polarization of field stars around 52 Cepheids found in recent surveys toward the Galactic plane. The Cepheids are located at the galactic longitudes $-10^{\circ} \le l \le +10.^{\!\!\!\circ }5$ and latitudes $-0.^{\!\!\!\circ }22\le b \le +0.^{\!\!\!\circ }45$, and their distances are mainly in the range of 10 to 15 kpc from the Sun. Simple classification of the sightlines is made with the polarization behavior vs. $H-K_{\mathrm{S}}$ color of field stars, and typical examples of three types are presented. Then, division of the field stars in each line of sight into (a) foreground, (b) bulge, and (c) background is made with the Gaia DR2 catalog, the peak of the $H-K_{\mathrm{S}}$ color histogram, and $H-K_{\mathrm{S}}$ colors consistent with the distance of the Cepheid in the center, respectively. Differential analysis between them enables us to examine the magnetic field structure more definitely than just relying on the $H-K_{\mathrm{S}}$ color difference. In one line of sight, the magnetic field is nearly parallel to the Galactic plane and well aligned all the way from the Sun to the Cepheid position on the other side of the Galactic center. Contrary to our preconceived ideas, however, sightlines having such well-aligned magnetic fields in the Galactic plane are rather small in number. At least 36 Cepheid fields indicate random magnetic field components are significant. Two Cepheid fields indicate that the magnetic field orientation changes more than $45^{\circ }$ in the line of sight. The polarization increase per color change $\Delta P/\Delta (H-K_{\mathrm{S}})$ varies from region to region, reflecting the change in the ratio of the magnetic field strength and the turbulence strength.


1987 ◽  
Vol 92 ◽  
pp. 82-83 ◽  
Author(s):  
C. T. Bolton ◽  
A. W. Fullerton ◽  
D. Bohlender ◽  
J. D. Landstreet ◽  
D. R. Gies

Over the past two years, we have obtained high resolution high signal/noise (S/N) spectra of the magnetic Be star σ Ori E at the Canada-France-Hawaii Telescope and McDonald Observatory. These spectra, which cover the spectral regions 399-417.5 and 440-458.5 nm and the Hα line and have typical S/N>200 and spectral resolution ≃0.02 nm, were obtained at a variety of rotational phases in order to study the magnetic field structure, the distribution of elements in the photosphere, and the effects of the magnetic field on the emission envelope. Our analysis of these spectra confirms, refines and extends the results obtained by Landstreet & Borra (1978), Groote & Hunger (1982 and references therein), and Nakajima (1985).The Hα emission is usually double-peaked, but it undergoes remarkable variations with the 1.19081 d rotational period of the star, which show that the emitting gas is localized into two regions which co-rotate with the star.


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